We propose to use ultrastructural, electrophysiological, and "metabolic cooperation" techniques to study factors that influence the formation of gap junctions between cultured Novikoff hepatoma cells. In addition we are testing the hypothesis that cyclic nucleotides can be transferred by way of junctions between cultured cells. BIBLIOGRAPHIC REFERENCES: Epstein, M.L., Sheridan, J.D., & Johnson, R.G. (1977). Formation of low-resistance junctions in vitro in the absence of protein synthesis and ATP production. Exptl. Cell Res., 104:25-30. Sheridan, J.D. (1977). Junction formation and experimental modification. In: Intercellular Junctions and Synapses in Development. Ed. J. Feldman, N.B. Gilula, & J.D. Pitts, Chapman & Hall, pub., London, in press.